AN ACR MLG MADE A NAV ERROR CAUSING LTSS AND GREAT CTLR HEARTBURN.

Narrative

WE WERE CLRED THE VOLLS 3 STAR TO BNA; RQZ TRANSITION; CLRED TO MAINTAIN 17000 FT. THE FO WAS FLYING. THIS WAS A SHORT FLT FROM HSV. APCHING RQZ I WAS GETTING BUSY SETTING UP ATIS FREQ AND RECEIVING COMPANY LNDG DATA. THE FO WAS EXTRA BUSY DUE TO THE AUTO THROTTLE SYS BEING INOP. I HAD BNA 135 DEG RADIAL INBOUND SET UP ON MY NAV RECEIVER. THE FO WAS TRACKING DIRECT TO RQZ. AS WE CROSSED RQZ; THE FO MISTOOK RQZ FOR BEING OVER VANDD INTXN AND TURNED L TO INTERCEPT BNA 135 DEG RADIAL INBOUND. NEITHER OF US CAUGHT THE MISTAKE DUE TO OUR WORKLOAD. ATC CALLED AND TOLD US TO TURN R TO HDG 040 DEGS TO INTERCEPT 135 DEGS BNA INBOUND. I ANSWERED AND WE STARTED THE TURN. ATC ISSUED A TURN TO AN ACR Y FLT. ATC THEN CAME BACK TO US AND TOLD US TO EXPEDITE OUR TURN TO 040 DEGS. WE WERE IN A 25 DEG BANK TURN GOING THROUGH ABOUT 005 DEGS AND I RESPONDED THAT WE WERE IN THE TURN. ATC'S NEXT XMISSION WAS BLOCKED BY ANOTHER ACFT. A FEW SECONDS LATER; HE CAME TO US WITH A REPEAT OF THE BLOCKED XMISSION; WITH A CLRNC TO LEVEL OFF AT 15000 FT. WE WERE CLBING THROUGH 15500 FT AT THE TIME SO WE DSNDED BACK TO 15000 FT. ABOUT THIS TIME WE WERE ROLLING OUT ON 040 DEG HDG. I RESET RQZ IN MY NAV FOR DME AND IT READ 15 DME TO NNE RQZ. LATER THAT DAY; I CALLED AND TALKED TO MEMPHIS CTR ON THE PHONE. WE APPARENTLY GOT TO 4.8 MI LATERAL SEPARATION WITH THE ACR Y FLT; WHICH TRIGGERED A TA AT THE CTR. I FEEL THE INCREASED WORKLOAD OF HAVING THE AUTO THROTTLES INOP ON A SHORT FLT WHICH HAS AN INCREASED WORKLOAD FOR A 2 MAN CREW ALREADY; CONTRIBUTED GREATLY TO ONE OR BOTH OF US NOT RECOGNIZING OUR ERROR ON THE STAR. I FEEL ALL AUTO SYS ON A 2 MAN ACFT SHOULD BE A MANDATORY FIX WHEN INOP. I ALSO FEEL THAT HAVING TCASII SHOW THE ACR Y FLT 5 MI AWAY WE WERE NEVER IN DANGER OF A CONFLICT; CONSIDERING WE WERE TAKING CORRECTIVE ACTION. SUPPLEMENTAL INFO FROM ACN 246145: MANUALLY FLYING IS NECESSARY TO STAY PROFICIENT; ALMOST ALL EMER PROCS REQUIRE SOME NON AUTOPLT FLYING. INOP AUTO THROTTLES COMPLETELY CHANGED MY COCKPIT HABIT PATTERNS. AUTOMATION HAS VASTLY ALTERED THE WAY WE FLY ACFT. WHEN A MAJOR COMPONENT BECOMES INOP; NORMAL HABIT PATTERNS CAN BE ALTERED TO THE POINT THAT THE CREW MEMBER EFFECTIVENESS IS DECREASED.